CONFUSED ABOUT PROJECTORS? Let us help clarify the situation here with a brief run down of some projector technology explained.
PROJECTOR RESOLUTION: This is the native resolution and is measured in pixels. A pixel is an abbreviation for "picture element" and is the smallest unit that a screen is capable of displaying. These are built up in a grid which then constitutes the picture. There are many different formats out there with two aspect ratios:- 4:3 (standard TV), 16:10 (widescreen format). For standard aspect ratios SVGA & XGA are the the two most common projector resolutions. SXGA & UXGA also exist although only in higher end projectors at the moment. The table below shows the pixel size of all the resolutions. Widescreen formats currently available are WXGA, WXGA+, WSXGA+ and WUXGA. These also tend to be be more expensive units.
RESOLUTIONS IN PIXELS
|SVGA is 800 x 600
XGA is 1024 x 768
SXGA is 1280 x 1024
SXGA+ is 1400 x 1050
UXGA is 1600 x 1200
WXGA is 1280 x 800
ANSI LUMENS: This is the measurement of brightness as defined by the American National Standards Institute (ANSI). It can be used as a guide for brightness but the rating is not absolute. We have found there to be a large variation in actual perceived brightness between units, with decent 1500 lumens projectors being effectively brighter than cheap 2500 lumens units. For this reason we only stock high quality projectors. When we sell projectors we recommend quality over bargain prices, although we can supply any make or model desired.
KEYSTONE / KEYSTONE CORRECTION: The keystone effect happens when the projector is not placed optimally to the screen. The lens should be on a line drawn at a right angle out from the centre of the screen. Optimal horizontal alignment is setting the bottom of the lens and at bottom of the screen in line. If, for instance, the projector is placed below the screen the resulting image will be wider at the top than the bottom which is known as vertical keystoning. This can be corrected digitally if the projector has the facility. All our hire stock has at least vertical keystone adjustment. Some of our models also allow for horizontal keystone adjustment. Please ask if you are unsure.
PROJECTOR - DISTANCE TO SCREEN & ZOOM LENS: For a 6 foot wide image the projector should be placed 12 feet back, ie. twice as far back as the image is wide. This can be adjuested using the zoom lens. Most modern projectors will also allow digital zooming for further adjustment if required.
PROJECTION TECHNOLOGIES - LCD, DLP & LCOS: These are the methods used to convert your image from an electrical / digital signal into an image. There are three competing technologies at this time which utilise different methodology to convert the light emitted by the internal lamp into a colour image on the screen. LCD projectors split white light into its primary component colour streams of red, green & blue using dichroic mirrors which are then shone through the LCD panels & recombined. By controlling the level of R, G & B on each pixel the colour of that pixel is created. DLP uses a grid of tiny mirrors, each corresponding to a pixel, which allow a given percentage of light through per pixel. This light is then shone through a rotating RGB colour wheel to bring colour into the equation. High end DLP projectors can use RGB split technology. LCOS is the newest of the three which is Liquid crystal on Silicon. It is almost a hybrid between the two technologies. At this time LCD is by far the market leader, with the brightest & clearest images although DLP is used in the home theatre market due to its improved contrast ratio. DLP can can problematic for some viewers due to the so-called Rainbow effect resulting in headaches & eystrain. LCOS is a relative newcomer to the field and may well go on to become the future of projection technology. We stock LCD projectors at this time although we can sell or provide rental DLP & LCOS units upon request.
PROJECTOR CONTROL: Most modern projectors will have an infrared remote offering at least basic functionality, plus full on board control. It is very common to also have USB control inputs which allow projector control from from a computer (appropriate driver disks will be required). Ethernet network control is also possible. Certain projector models have on board DVD players, and or MPEG players meaning that an external input is unnecessary.
PROJECTOR INPUTS: Most projectors will accept a number of different inputs. PAL, SECAM & NTSC are generally accepted. Composite & S-Video are generally accepted as are computer monitor style inputs on 15 pin d-sub connectors. DVI (Digital Video Interface) is now widely accepted.